In one type of commonly used HVAC system 110, shown in FIG. 1, an actuator-driven valve 112 modulates a flow of a fluid media, such as water, from a source 114 of hot and/or cold fluid to a heat exchanger 116, for heating and/or cooling a conditioned space 118 (to the left of dashed line 120 in FIG. 1). The valve 112 is controlled by an actuator 112 that is operatively attached to the valve 112. The actuator 122 controls the valve 112 in accordance with control signals 124 transmitted to the actuator 122 from a controller 126, such as a typical wall mounted thermostat, mounted in the conditioned space 118. The controller 126 has an input device, such as a knob, a keypad, or buttons that allow a person to input a desired room temperature to the controller 126. The controller also typically includes an internal temperature sensor, for sensing the current room temperature of the space 118.
The source 114 of hot and cold fluid is generally mounted outside of the conditioned space 118. The source 114 of hot and cold fluid is typically a centralized supply circuit, having a single boiler and chiller unit that can be alternately connected within the source 114, for supplying hot or cold fluid to multiple conditioned spaces 118, as indicated by dashed lines in FIG. 1, with each space 118 including its own separate heat exchanger, actuator-driven valve, and controller, operating as described above for controlling the temperature of that particular space, using hot or cold fluid from the centralized source 114.
When it is desired to operate the HVAC system 110 in a heating mode, the source 114 is configured to provide hot fluid. For a typical system using water as the fluid media, hot water is provided at a temperature of about 95 degrees Fahrenheit when the HVAC system 110 is operating in a heating mode. In the heating mode, the controller 126 and actuator 122 are configured to operate in a reverse actuation mode, in which the actuator 122 drives the valve 112 toward a closed position, to reduce the flow of hot fluid to the heat exchanger 116 when the room temperature rises above the desired temperature for the space, and when the room temperature drops below the desired temperature for the space 118, the actuator 122 drives the valve 112 toward an open position, to increase the flow of hot fluid to the heat exchanger 116.
When it is desired to operate the HVAC system 110 in a cooling mode, the source 114 is configured to provide cold fluid. For a typical system using water as the fluid media, cold water is provided at a temperature of about 55 degrees Fahrenheit when the HVAC system 110 is operating in a cooling mode. In the cooling mode, the controller 126 and actuator 122 are configured to operate in a direct actuation mode, in which the actuator 122 drives the valve 112 toward an open position, to increase the flow of cold fluid to the heat exchanger 116, when the room temperature rises above the desired temperature for the space, and when the room temperature drops below the desired temperature for the space 118, the actuator 122 drives the valve 112 toward a closed position, to reduce the flow of cold fluid to the heat exchanger 116.
The changeover between heating and cooling modes typically takes place only twice a year, in the spring and fall, and generally requires some degree of manual reconfiguring of operating components (not shown), such as valves, or switches, within the source 114. The changeover may also involve more complex activities within the source, such as starting or shutting down a boiler used for heating the fluid during operation in the heating mode, and concurrently shutting down or starting a chiller used for cooling the fluid during operation in the cooling mode.
The changeover between heating and cooling modes also requires re-configuring the controller 126 and actuator 122 in each of the spaces 118, to change from reverse actuation mode to direct actuation mode when the HVAC system 110 is changed from heating to cooling mode, and conversely to change from direct actuation mode to reverse actuation mode when the HVAC system 110 is changed from cooling to heating mode. If the actuation mode is not properly reconfigured to match the operating mode of the source 114, the HVAC system 110 will operate backwards from the way it should.
For example, if the controller 126 and actuator 122 are left in the direct actuation mode with the source 114 in heating mode, the valve 112 will open wider and supply more hot fluid to the space 118 when the room temperature rises above the desired temperature, and will close down and supply less hot fluid to the space when the room temperature drops below the desired temperature. The result of this being that the space 118 becomes hotter and hotter, or colder and colder, once the HVAC system 110 turns on, and never reaches the desired temperature through operation of the HVAC system 110.
Conversely, if the controller 126 and actuator 122 are left in the reverse actuation mode with the source 114 in cooling mode, the valve 112 will close down and supply less cold fluid to the space 118 when the room temperature rises above the desired temperature, and will open further and supply more cold fluid to the space when the room temperature drops below the desired temperature. The result of this once again being that the space 118 becomes hotter and hotter, or colder and colder, once the HVAC system 110 turns on, and never reaches the desired temperature through operation of the HVAC system 110.
Historically, in order to keep the actuation mode in proper relationship to the operating mode of the HVAC system 110, it was necessary to physically change the position of switches, jumpers, or wires on the controllers 126 and/or actuators 122 in each of the spaces 118 when the operating mode of the source 114 was changed. Having to reconfigure the controllers 126 and/or actuators 122 in each space 118 is obviously time consuming, and fraught with opportunity for missing one of more spaces 118 in an HVAC system 110 serving a large multi-unit building. It is also intrusive to the occupants of the spaces 118, for someone to have to enter their space 118 twice a year to reconfigure the controller 126 and/or actuator 122.
In addition, the change of seasons is often unpredictable. A sudden heat wave after a building is switched over to heating mode, or a cold spell after switching to cooling mode, can leave the occupants of the spaces 118 without the ability to set the room temperature at a comfortable level. Even if the operating mode of the source 114 were to be changed back, as a result of the sudden heat or cold spell, it would be necessary to re-enter all of the spaces 118 to reconfigure the controllers 126 and/or actuators 122 accordingly, and then repeat the reconfiguration process yet again, for the source 114 and controllers 126 and/or actuators 122 when the sudden hot or cold spell had passed. Normally, building operators will not want to expend all of this effort during an unseasonable hot or cold spell, thereby leaving the occupants of the spaces 188 without the ability to set the room temperature of their space 118 at a comfortable level, until the hot or cold spell has passed.
It is desirable, therefore to have an apparatus and method for automatically reconfiguring the controllers 126 and/or actuators 122 in each space 118 when the operating mode of the source 114 is changed from heating to cooling or vice versa.
FIG. 2 shows a prior approach to addressing the problems discussed above, by providing an apparatus and method for automatically reconfiguring the controllers 126 and/or actuators 122 in each space 118 when the operating mode of the source 114 is changed from heating to cooling or vice versa. In the apparatus shown in FIG. 2, a temperature sensor or thermostatically operated switch 128 is attached to a pipe 130, at a point upstream from each of the heat exchangers 116 in the HVAC system 110. The temperature sensor or switch 128 associated with each heat exchanger 116 generates a temperature signal 132, indicative of whether the source 114 is supplying hot or cold fluid to that heat exchanger 116. The temperature signal 132 from each temperature sensor or switch 128 is transmitted over a separate set of wires 134 to the controller 126 in the space 118 served by the particular heat exchanger 116 associated with that temperature sensor or switch 128. The controller 126 and/or actuator 122 in the space 118 served by that heat exchanger 116 are operatively configured to receive the temperature signal 132 from the temperature sensor 128 associated with the heat exchanger 116 serving that particular space 118, and determine whether the source 114 is currently configured for supplying hot or cold fluid to that space 118. The actuator 122 is then controlled in the direct actuation mode if the cold fluid, or alternatively in the reverse actuation mode, it the source 114 is currently configured for supplying hot fluid.
While the prior apparatus and method, described above and shown in FIG. 2, generally work well for the intended purpose of automatically reconfiguring the controller 126 and or actuator 122 when the HVAC system 110 operating mode is changed, there are several areas in which further improvement is desirable. It is cumbersome and time consuming to have to individually attach the temperature sensors 128 to the piping serving the heat exchangers 116, and run the wires back to the appropriate controller 126. Reliability is also somewhat reduced, in that the sensor 128 and the separate set of wires 134 for each space 118 are exposed and vulnerable to damage. In particular, if it should be necessary to make any plumbing repairs to the piping supplying fluid to the heat exchanger 116, the sensor 128 may need to be removed and reattached to a new section of pipe, or so that it is not damaged by heating the pipe during sweat soldering which may be required in making the repairs.
It is desirable, therefore, to provide an improved apparatus and method addressing the problems described above, for automatically reconfiguring the controller 126 and or actuator 122 when the operating mode of the HVAC system 110 is changed.